According to recent studies, male infertility is responsible almost 40% of the time that a couple is unable to conceive a child. By convention, male infertility is diagnosed based on low sperm motility and/or count. When no sperm are observed to move in a sample obtained from a male, that male is diagnosed as being infertile. However, besides zero motility, there are really no motility thresholds for distinguishing fertile sperm from infertile sperm. With regard to sperm count, twenty million sperm per milliliter or greater is generally considered to be in the fertile range. Sperm count and motility can be assessed using commercially available instruments, such as computerized videoanalysis systems.
U.S. Pat. No. 5,068,089 describes a home kit for testing fertility of human sperm, based on ability of the sperm to reduce a dye. The extent of reduction (displayed calorimetrically), is said to be indicative of sperm fertilizing ability. However, this test is complicated to perform, requires incubation at a temperature above room temperature and does not distinguish between reduction due to sperm cells or other cells, which may be present in a semen sample.
U.S. Pat. No. 5,219,729 describes a laboratory assay for determining the fertilizing ability of sperm based on the affinity of binding between to a oocyte zona pellucida fragment. The tighter the binding, the greater the fertilizing ability of the sperm sample. However, this assay requires freshly prepared oocyte fragments and at least four hour's time during which the sperm must be kept in contact with the oocyte fragment.
A simple and rapid assay for determining the pregnancy potential of sperm in a laboratory or at home is needed.